24 hours. This is very helpful for daylight savings time:

	select '2005-05-03 00:00:00 EST'::timestamp with time zone + '24 hours';
	      ?column?
	----------------------
	2005-05-04 01:00:00-04

	select '2005-05-03 00:00:00 EST'::timestamp with time zone + '1 day';
	      ?column?
	----------------------
	2005-05-04 01:00:00-04

Michael Glaesemann